Level gauges are often used to measure the fluid level of a tank or vessel, particularly in an industrial process environment. One such type of level gauge is a magnetic level indicator, which typically comprises a non-magnetic chamber, a float, and a visual level indicator. The chamber is typically a vertically mounted pipe that is connected to a tank or vessel by one or more pipes. Typically, one connecting pipe forms a connection between the top of the chamber and the top of the vessel and the other connecting pipe forms a connection between the bottom of the chamber and the bottom of the vessel. This arrangement permits the fluid level in the chamber to equalize with the fluid level in the tank. The float, as the name implies, floats at the surface of the fluid, rising and falling with the fluid. The float also contains one or more magnets for actuating the visual level indicator on the outside of the chamber.
Many visual level indicators comprise an elongated level indicator tube having a magnetically operated visual indicator sealed inside it. The magnetically operated visual indicator typically has a plurality of flags. The flags usually contain an alignment magnet that couples with the float magnet as the float moves up or down within the chamber. The movement of the float actuates the flags and changes their color to indicate the fluid level in the vessel. Typically, color is changed by causing the flags to rotate so opposing and differently colored sides are displayed.
In the prior art, the magnetically operated visual indicator is typically integral with the visual level indicator, i.e., the magnetically operated visual indicator typically cannot move within the elongated level indicator tube of the visual level indicator. This arrangement can be problematic because the magnetically operated visual indicator typically expands or contracts in response to temperature changes, which can cause the magnetically operated visual indicator to twist or flex. Such twisting or flexing can damage or deform the magnetically operated visual indicator, which can lead to process downtime. In addition, if the level gauge is non-functional or completely removed, then process safety issues can arise, e.g., overfilling of a tank, inadequate volume of a process fluid for an emergency cooling system, and so forth.
Prior art elongated level indicator tubes are typically sealed to keep condensation or other contaminants out of the housing. The tube is typically sealed along its circumference using traditional glassblowing techniques or a sealant (e.g., caulk, adhesive, plugs with o-rings, etc.). However, using traditional sealing or glassblowing techniques can be problematic because such techniques can weaken the integrity of the elongated level indicator tube making it more likely that the elongated level indicator tube could become damaged if it is twisted or flexed during assembly or use. Likewise, breakage during shipping and handling is more likely if the glass has been stressed.
Therefore, in view of the above, a need exists for an apparatus and method that can overcome one or more of the problems discussed above.